The present disclosure relates to directional or steerable beam antennas, of the type employed in such applications as radar and communications. More specifically, it relates to a dielectric waveguide antenna, in which an evanescent coupling geometry is controllably altered by switchable elements in an evanescent coupling edge, whereby the geometry of the transmitted and/or received beam is controllably altered to achieve the desired directional beam configuration and orientation.
Steerable antennas, particularly dielectric waveguide antennas, are used to send and receive steerable millimeter wave beams in various types of radar devices, such as collision avoidance radars. In such antennas, an antenna element includes an evanescent coupling edge having a selectively variable coupling geometry. The coupling edge is placed substantially parallel and closely adjacent to a transmission line, such as a dielectric waveguide. As a result of evanescent coupling between the transmission line and the antenna elements, electromagnetic radiation is transmitted or received by the antenna. The shape and direction of the transmitted or received beam are determined by the selected coupling geometry of the evanescent coupling edge, as determined, in turn, by the pattern of electrical connections that is selected for the edge features of the coupling edge. This pattern of electrical connections may be controllably selected and varied by an array switches that selectively connect the edge features. Any of several types of switches integrated into the structure of the antenna element may be used for this purpose, such as, for example, semiconductor plasma switches. See, for example. U.S. Pat. No. 7,151,499 (commonly assigned to the assignee of the present application), the disclosure of which patent is incorporated herein by reference in its entirety. A specific example of an evanescent coupling antenna in which the geometry of the coupling edge is controllably varied by semiconductor plasma switches is disclosed and claimed in the commonly-assigned, co-pending U.S. Patent Application Publication No. 2009/0121804, the disclosure of which is incorporated herein in its entirety.
While the technology disclosed and claimed in the aforementioned U.S. Pat. No. 7,151,499 and Application Publication No. 2009/0121804 are improvements in the state of the art, it would be advantageous to provide still further improvements, such as those that could provide the advantages of lower fabrication costs and reduced parasitic coupling among the several components of the antenna array.